Conversion from a natural mineral to a novel effective adsorbent: Utilization of pumice grafted with polymer brush for methylene blue decolorization from aqueous environments

Abstract

The present work reports the adsorption yield of methylene blue (MB) from aqueous environments using pumice (PMC) coated with poly(N-[Tris (hydroxymethyl)methyl]acrylamide), PTHAM@PMC, by surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization. The synthesized PTHAM@PMC particles were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR), scanning electron microscopy (SEM) and water contact angle measurements. Results revealed that a homogeneous polymer layer was grafted on the PMC surface. Response surface methodology (RSM) with central composite design (CCD) was performed to optimize and to investigate the influence of independent parameters such as initial pH, initial MB concentration (Co, mg/L), adsorbent dosage (m, mg), contact time (t, min) and temperature (T, °C) for MB% removal with PTHAM@PMC. The results based on CCD indicated that the optimum initial pH, Co, m, t and T are 8.95, 52.53 mg/L, 40.5 mg, 67.28 min and 33.52 °C, respectively. The maximum removal efficiency of 98.68% and the maximum adsorption capacity of 68.998 mg/g were reached at these optimal points. Additionally, the kinetic, isotherm and thermodynamic studies were performed and the obtained results were evaluated. The great advantage of this work is that polymer brush grafted pumice had high adsorption capacity, fast adsorption kinetics, and high removal of MB. Considering all of these, it is thought that the constructed pumice with polymer brush will allow the improvement of novel procedures for the adsorption process.